1. Field of the Invention
The present invention relates to a drill and, more particularly, to a bone implant drill that is suitable for a bone implant and that can be coupled with a drilling machine to proceed with a drilling operation for bone implantation.
2. Description of the Related Art
During a dental implant surgery, the surgeon generally drills a hole in the alveolar bone of a patient before tightly implanting an implant into the alveolar bone. In a dental implant surgery of an upper jaw, in a case that the height of the bone ridge of the upper jaw of the patient is insufficient, it is necessary to lift the sinus membrane of the patient and to graft bone before implanting the implant, avoiding the implant from penetrating the sinus membrane. Such a surgery is referred to as a sinus lifting operation.
The sinus lifting operation includes two commonly used methods: a window method and a bone chisel method. The operation is decided by the residual height of the alveolar bone. Namely, the window method requiring a longer treatment time is adopted if the residual height of the alveolar bone is smaller than 5 mm. The bone chisel method can be used if the residual height of the alveolar bone is equal to or larger than 5 mm.
Specifically, the bone chisel method includes using a hammer to strike a bone chisel, causing perforating fracture at the bottom of the paranasal sinus by hammering. An edge of a recessed portion in a top end of the bone chisel is used to scrape the ambient bone into the paranasal sinus. The bone scraps protect the sinus membrane from tear and perforation during lifting of the paranasal sinus. Furthermore, the autogenous bone is helpful in generation of a new bone without the need of obtaining a bone, reducing the loss of the autogenous bone. The costs are reduced, because artificial bone implantation is not required.
To avoid the sinus membrane of the patient from being broken by the bone chisel, the surgeon generally proceeds a preoperative planning by computerized tomography to check the height and density of the bone. However, operation of the bone chisel method largely relies on the experience and the hand feel of the surgeon, and it is not uncommon that the patient suffers from clinical aftereffects including dizziness or even concussion due to an excessive hammering force.
FIG. 1 shows a conventional bone implant drill 9 including a column 91, a transmission shaft 92, an elastic element 93, and a sealing member 94. A cutter 911 is provided on an end of the column 91. A coupling seat 912 is provided on the other end of the column 91. A transmission seat 921 is provided on an end of the transmission shaft 92 for meshing with a toothed portion of the coupling seat 912. The other end of the transmission shaft 92 can be coupled to an electric hand piece H for driving the transmission shaft 92 to rotate. Two ends of the elastic element 93 are respectively connected to the coupling seat 912 and the transmission seat 921. The sealing member 94 envelops the coupling seat 912, the elastic element 93, and the transmission seat 921.
When the cutter 911 encounters a resistance, the transmission seat 921 compresses the elastic element 93 and engage with the coupling seat 921, causing synchronous rotation of the column 91. The resistance exerting on the cutter vanishes at the moment the cutter 911 penetrates the cortical bone, and the elastic element 93 immediately disengages the transmission seat 921 from the coupling seat 912 such that the transmission shaft 92 no longer rotates jointly with the column 91, effectively avoiding the cutter 911 from keeping cutting and, hence, injuring the nasal membrane of the patient. An example of such a bone implant drill is disclosed in US Patent Publication No. 2013/0171585 entitled “APPARATUS FOR LIFTING MAXILLARY SINUS”.
However, the two ends of the elastic element 93 of the conventional bone implant drill 9 directly abut an interior of the coupling seat 912 and an interior of the transmission seat 921, such that the moment the elastic element 93 disengages the transmission seat 921 from the coupling seat 912, a speed difference is generated between the column 91 that stops rotating and the elastic element 93 that still rotates jointly with the transmission shaft 92 at a high speed (normally higher than 2000 rpm). Thus, heat is generated due to the friction between an end of the elastic element 93 and the coupling seat 912. As a result, the column 91 directly contacting the bone cells is apt to be in a high temperature state. Ostenonecrosis resulting from bone necrosis fever is apt to occur if the contact temperature exceeds 60□. Although water spray can be provided to reduce the temperature of the outer portion of the column 91 to be below 60□, the cutter 911 of the column 91 still has the risk of excessively high temperature.
Furthermore, the high temperature resulting from friction also adversely affects the function of the elastic element 93. Thus, the elastic element 93 whose elasticity has been compromised in the previous high-temperature operation cannot reliably disengage the transmission seat 921 from the coupling seat 912 at the moment the cutter 911 of the column 91 penetrates the cortical bone, such that the column 91 keeps rotating and injures the nasal membrane of the patient by the cutter 911. Thus, the conventional bone implant drill 9 cannot operate continuously and, thus, provides poor use convenience.
Furthermore, the elastic element 93 is not supported from the inside and is, thus, liable to twist and deform, failing to disengage the transmission seat 921 from the coupling seat 912. The twisted and deformed elastic element 93 could even hook the toothed portion of the transmission seat 921 such that the column 91 cannot stop rotating at the moment the cutter 91 penetrates the cortical bone, which also results in injury to the nasal membrane of the patient.
Furthermore, the speed difference between the column 91 and the elastic element 93 tends to wear the coupling seat 912 or damage the elastic element 93 after a long period of time of use. The service life of the conventional bone implant drill 9 is, thus, adversely affected.
Thus, improvement to the conventional bone implant drills is required.